Dr. Thomas Montine, University of Washington, autopsied the brains of 3,400 men and women who had experienced cognitive decline and dementia.

45% of the risk for dementia was associated with pathologic changes of Alzheimer’s disease.

10% of dementia risk was associated with Lewy bodies (neocortical structural changes that indicate a degenerative brain disease known as Lewy Body Dementia–believed by some to be a variant of Alzheimer’s and/or Parkinson’s disease).

33% was associated with damage to the brain from small vessel disease.

Small vessel damage is the cumulative effect of multiple small strokes caused by hypertension and diabetes–strokes so small that the person experiences no sensation or problems until the cumulative effect reaches a tipping point.

The good news is that prevention and treatment for small vessel disease is often caused by complications of hypertension and diabetes, which are diseases with available treatments.

Although, Dr. Montine’s findings differ from common wisdom and previous brain autopsy studies, he feels that the broad population of subjects, from the Seattle region, overcomes the limitations of previous studies that studied either one gender, ethnic group, or professional group. Individuals in this study were part of the Group Health Cooperative, one of the oldest and largest managed care programs in the United States.

The unexpected finding that one-third of the risk for dementia is related to small vessel disease also provides an additional reason to control hypertension and diabetes.